MySQL Convertir une chaîne à ce jour Calculer l'âge et trier par âge

SELECT  EXTRACT(YEAR FROM (FROM_DAYS(DATEDIFF(NOW(),STR_TO_DATE(birthday, '%m/%d/%Y'))))) + 0 age,
        COUNT(*) TotalCount
FROM    tableNAme
GROUP   BY EXTRACT(YEAR FROM (FROM_DAYS(DATEDIFF(NOW(),STR_TO_DATE(birthday, '%m/%d/%Y'))))) + 0
ORDER   BY TotalCount DESC

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